Each column in this table lets you define rule weights for different 'conditions'. The conditions are set by the spam filter scripts.
Internally, the spam filter scripting system allows you have as many different 'conditions' as you wish. The default spam filter rules only define two - when the Bayesian analyser thinks the chance of a message being spam is <=90% and when it thinks it's >90%, but custom rules may define as many as they want.
If a spam rule definition defines more than 2 default weight values then VPOP3 will expand all rules to match that number of values (by copying the last number)
If you have more than two columns it is possible that either at some point in the past you have had a rule which has had more than two default weight values and VPOP3 has expanded the table accordingly, or the spam configuration file has been corrupted slightly so it has more than two values.
If you wish to set the spam filter configuration back to the default, you can stop VPOP3, delete the 'spamconfig.txt' file in the VPOP3 directory and restart VPOP3. That will set the rule weights and script configuration to the default settings and should set it back to two columns.